192
•
If the tracked object functions normally, for example, the target interface is up or the target network
is reachable, the state of the track entry is Positive.
•
If the tracked object functions abnormally, for example, the target interface is down or the target
network is unreachable, the state of the track entry is Negative.
•
If the detection result is not valid, for example, the NQA test group that is associated with the track
entry does not exist, the state of the track entry is Invalid.
The following detection modules can be associated with the track module:
•
NQA
•
BFD
•
Interface management module
Collaboration between the track module and an application module
When the status of the track entry changes, the track module notifies the associated application module,
which then takes proper actions.
The following application modules can be associated with the track module:
•
Virtual Router Redundancy Protocol (VRRP)
•
Static routing
•
Policy-based routing
In some cases, when the status of a track entry changes, if the track module immediately notifies the
application modules, communication may be interrupted because routes cannot be recovered in time.
For example, the master in a VRRP group monitors the uplink interface through the track module. When
the uplink interface fails, the track module notifies the master to reduce its priority so that a backup with
a higher priority can preempt as the master to forward packets. When the uplink interface recovers, if the
track module immediately notifies the original master to restore its priority, the master will immediately
forward packets; however, the uplink route has not been recovered yet, which may result in packet
forwarding failure. Then configure the track module to notify the application modules of the track entry
status change after a specified delay time.
Collaboration application example
The following is an example of collaboration between NQA, track, and static routing.
Configure a static route with next hop 192.168.0.88 on the device. If the next hop is reachable, the static
route is valid. If the next hop becomes unreachable, the static route should become invalid. For this
purpose, configure collaboration between the NQA, track, and static routing modules:
1.
Create an NQA test group to monitor the reachability of IP address 192.168.0.88.
2.
Create a track entry and associate it with the NQA test group. When the next hop 192.168.0.88
is reachable, the track entry is in the Positive state. When the next hop becomes unreachable, the
track entry is in the Negative state.
3.
Associate the track entry with the static route. When the track entry turns to the Positive state, the
static route is valid. When the associated track entry turns to the Negative state, the static route is
invalid.
Track configuration task list
To implement the collaboration function, establish associations between the track module and the
detection modules, and between the track module and the application modules.
